How Much Protein?

By William Misner, Ph.D.

The more prolonged or intense the exercise, the more protein
the body cannibalizes for energy from the working muscles.

Researchers measured the protein-calorie cost of exercise to
be between 6% and 15% of the total energy expense each hour. Proteins
metabolized from lean muscle stores are rate-limited (regulated) by the release
of specific enzymes. For example, Leucine, a branch chain amino acid (BCAA), oxididation rate is controlled by the enzyme, Branched-Chain Oxo-Acid-Dehydrogenase (BCOAD). This enzyme is relatively low at rest (4-7%), but during exercise,
dephosphorylation releases it to as high as +25%. After exercise, both BCOAD
and Leucine oxidation are attenuated, though total BCOAD is up-regulated.[2]
Some research utilize higher amino acid catabolism, (+15%) during endurance
exercise.[3]
It is conceded that as pace increases from slow aerobic to faster anaerobic,
the % of amino acids burned also increase. However, for this article, the
slower pace conservative 6% rate will be applied.[4]

If the diet is calorie sufficient, low exercise activity has
little impact on protein requirement; a 1.0 gram/protein per kg/day is
sufficient. However, most endurance athletes require more dietary protein
intake for 3 reasons:

Insufficient
carbohydrate calories to meet energy expense

Insufficient
protein calories to meet energy expense

Exercise
training expenditure increases 10-fold above resting state

Studies confirm that both endurance and strength training
increase skeletal muscle protein synthesis (breakdown). Researchers using
nitrogen balance measuring technique confirm protein requirements for endurance
exercise is increased to between 1.2-1.4 g/kg bodyweight per day. The timing of
and nutritional content of the post-exercise meal is surprisingly overlooked.
The post-exercise meal can be manipulated to reproduce synergistic protein
accretion effects after exercise.[5]
However, this effect may not occur if the post-exercise protein content is
absent, poorly timed, especially if endurance duration and intensity create a
severe energy deficit.

THE MATH:
Each hour exercise metabolizes approximately 700 calories, 42 of which are
cannibalized from lean muscle amino acid stores (-10.6 grams protein/hour),
which need to be replaced immediately after the workout (See figure 1).

Research confirms that rate of recovery and muscle synthesis
rate are dramatically increased if amino acids and carbohydrates is consumed
together immediately after the exercise training. Intense training may increase
dietary protein requirements to as high as 1.7 grams protein per kilogram
bodyweight per day. Researchers was examined a group of Ultrarunners to see how
food absorbed effected blood chemistry during an extreme endurance event
running 50 km (31 miles/day) for 20 consecutive days. Changes in the muscle's
fat-free compartment and its relation to the corresponding biochemical and
nutritional parameters of 42 male and 13 female 1000k ultra runners initially increased, but decreased
in the middle phase, and stabilized for the rest of the run. Significant
changes in the fat-free weight occurred from the 11th day on; lean body mass
decreased until the middle of the distance runned; lean body mass rebound
increasing until the end. All the muscle-circumferences were reduced with the
exception of the thigh, which grew, paralleling the CK/CKMB-concentrations, a
phenomenon due to the high mechanical stress on the lower extremities. The
biochemical parameters exhibited a strain-related reaction of adaptation within
the initial 6 days, the hormones and protein-concentrations increasing in the
beginning and falling from the third day on, uric acid and CK/CKMB-activity
decreasing from the 6th day on. A consecutive parallel reduction of uric acid,
urea, and muscle measurements might be seen as a special endurance-related
clearance-mechanism of potential toxicants. The negative relationship between
the changes of muscle measurements and the cumulative protein intake and the
catabolic constellation of the clinical-chemical values might suggest that the
absolute protein intake of 1.7 g/kg body mass should be increased in order to
diminish the loss of musculature during an ultra-long distance run.[6]

PROTEIN TIMING

Timing of protein intake is important during and immediately after exercise. Biolo et al. reported that protein stimulates muscle protein synthesis more after exercise than before. IV-amino acid infusions (alanine, phenylalanine, leucine, and lysine) were given subjects during sedentary and post-exercise states. The muscle protein synthesis rate surprisingly increased +291% arterial amino acids after exercise compared to +141% increases from protein infusions given before exercise. Increases of +64% leg blood flow rate occurred after exercise above at rest levels. Amino acid transport increased 30-100% greater after exercise than before exercise. Dietary protein stimulates muscle protein synthesis more after exercise than before or during exercise. Partly this effect is due to enhanced blood flow. Protein consumed immediately after exercise reproduces a greater muscle growth effect than when consumed at any other time.[7]

ANABOLIC GROWTH FROM RESISTANCE TRAINING

Resistance exercise produces a net protein synthesis that may reverse age-associated muscle mass loss. As noted, muscle protein synthesis is synergistically influenced by post-exercise supplementation, but the importance of protein timing is needs to be resolved. Research examined the importance of immediate (p0) oral protein or delayed (p2) intake of an oral protein supplement upon muscle hypertrophy and strength during a period of resistance training in elderly males. Thirteen men (74 years; body mass index (BMI) of 24-26 kgm (-2) completed a 12-week resistance training program (3 times per week) receiving oral protein in liquid form of 10 g protein (42%), 7 g carbohydrate (29%), 3 g fat (28%) immediately following resistance training immediately after (p0) or 2-hours after (p2) each training session. Muscle hypertrophy was evaluated by magnetic resonance imaging (MRI) and from muscle biopsies. Muscle strength was determined using dynamic and isokinetic strength measurements. Body composition was determined from dual-energy X-ray absorptiometry (DEXA) and food records were obtained over 4 days. The plasma insulin response to protein supplementation was also determined. In response to training, the cross-sectional area of the muscle quadriceps femoris increased from 54.6 to 58.3 cm2 and mean fibre area increased from 4047 to 5019 microm2 in the post-exercise supplementation p0 group, whereas no significant increase was observed in p2. Post-exercise supplementation p0 dynamic and isokinetic strength increased by 46%, but p2 dynamic and isokinetic strength increased by only 15% and isokinetic strength by only 36%. No differences in glucose or insulin response were observed between protein intake at 0 and 2 hours post-exercise. This demonstrates that early intake of an oral protein supplement following resistance training is very important for skeletal muscles growth even in elderly males - muscle growth response after resistance training.[8]

SOLUTIONS TO EXERCISE-INDUCED
PROTEIN DEFICIENCY

Several sport scientists advocate a 4:1 ratio of protein to carbohydrate for muscle synthesis following exercise. Though the 4:1 ratio is popular and rational, a 3:1, 2:1, or 1:1 ratios need to be evaluated. The research report (above) in elderly subjects consumed only a 4:3 carbohydrate:protein during their post-exercise recovery intervention. Some researchers demonstrate that a higher dietary protein intake (up to 1.6 g protein kg (-1) d (-1)) in order to reproduce a hypertrophic response to resistance exercise. It has been demonstrated that very old men and women who consumed a protein supplement achieved a greater strength and muscle mass gain than those consuming a no-protein placebo. The important adage is to include adequate protein and carbohydrates immediately following exercise.[9][10] This may mean more protein and more carbohydrates should accompany exercise intensity increase.